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April 17, 2012 -- Treatment with testosterone may help heart failure patients feel better and exercise more, preliminary research shows.

The finding comes from four small studies of people with heart failure. The researchers analyzed the results from all of those studies and found that those who took testosterone supplements were able to exercise longer than those who didn't.

Testosterone occurs naturally in men and women. But testosterone levels decline with age, which can contribute to decreases in muscle mass and strength.

Though patients in the trials appeared to benefit from supplemental testosterone, larger and longer studies are needed to prove the treatment is safe and effective, says researcher Justin A. Ezekowitz, MD, who directs the Heart Function Clinic at the University of Alberta in Edmonton, Canada.

5 Million in U.S. Have Heart Failure

Heart failure is a leading cause of hospitalization in people over the age of 65 in the U.S.

About 5 million Americans have heart failure, and each year about half a million more get diagnosed with it, which means their hearts have a reduced capacity to pump blood efficiently.

When this happens, the heart can become enlarged, fluid may build up in the soft tissues and organs, and people typically become exhausted with exertion.

"Patients with heart failure don't feel very well, in part because they can't exercise," says Clyde Yancy, MD, chief of cardiology at Chicago's Northwestern Feinberg School of Medicine and a spokesman for the American Heart Association.

"The idea of a novel treatment approach that can help improve exercise capacity is very intriguing," he says.

The studies included nearly 200 patients, most of whom were men. They were 67 years old, on average.

About half the patients received testosterone by injection, patch, or gel, for as little as three months or as long as a year. The other half got a placebo.

The study appears in the journal Circulation.

Testosterone Patients Walked Farther

In two studies, the severity of heart failure improved more for patients who got testosterone treatment, compared to those who got a placebo.

When the trials were considered together, testosterone-treated patients scored 50% better on a six-minute walking test that checks exercise capacity.

"The improvement in exercise capacity was striking," Ezekowitz tells WebMD. "Patients in the testosterone group were generally able to walk longer than those in the placebo group."

But Yancy says the improvements seen in the four studies are better characterized as modest.

The testosterone-treated patients walked, on average, about 59 yards more than the other patients during the six-minute walking tests.

"That is the equivalent of one more lap up and down the hall," he tells WebMD. "That is not a huge improvement, and it is not clear that this is enough to help patients feel better long term."

Testosterone Safety Questioned

Yancy says it is also not clear if testosterone is a safe, long-term treatment for heart failure.

"We really don't understand the risks of taking extra testosterone in patients with heart failure, and given the small number of patients in these studies and the short follow-up, there is reason for concern," he says.

He adds that too few heart failure patients are taking existing treatments that could help them feel better and improve their ability to exercise.

"If more patients were treated with appropriate available therapies, exercise capacity would not be such a big issue," he says.